Revert "Revert "[LLDB][GUI] Expand selected thread tree item by default""

This reverts commit fd18f0e84c.

I reverted this change to see its effect on failing GUI tests on LLDB
Arm/AArch64 Linux buildbots. I could not find any evidence against this
particular change so reverting it back.

Differential Revision: https://reviews.llvm.org/D100243

lldb/source/Core/IOHandlerCursesGUI.cpp

@@ -3768,8 +3768,13 @@ public:
 
   virtual void TreeDelegateDrawTreeItem(TreeItem &item, Window &window) = 0;
   virtual void TreeDelegateGenerateChildren(TreeItem &item) = 0;
+  virtual void TreeDelegateUpdateSelection(TreeItem &root, int &selection_index,
+                                           TreeItem *&selected_item) {
+    return;
+  }
   virtual bool TreeDelegateItemSelected(
       TreeItem &item) = 0; // Return true if we need to update views
+  virtual bool TreeDelegateExpandRootByDefault() { return false; }
 };
 
 typedef std::shared_ptr<TreeDelegate> TreeDelegateSP;
@@ -3779,7 +3784,10 @@ public:
   TreeItem(TreeItem *parent, TreeDelegate &delegate, bool might_have_children)
       : m_parent(parent), m_delegate(delegate), m_user_data(nullptr),
         m_identifier(0), m_row_idx(-1), m_children(),
-        m_might_have_children(might_have_children), m_is_expanded(false) {}
+        m_might_have_children(might_have_children), m_is_expanded(false) {
+    if (m_parent == nullptr)
+      m_is_expanded = m_delegate.TreeDelegateExpandRootByDefault();
+  }
 
   TreeItem &operator=(const TreeItem &rhs) {
     if (this != &rhs) {
@@ -4008,6 +4016,8 @@ public:
       const int num_visible_rows = NumVisibleRows();
       m_num_rows = 0;
       m_root.CalculateRowIndexes(m_num_rows);
+      m_delegate_sp->TreeDelegateUpdateSelection(m_root, m_selected_row_idx,
+                                                 m_selected_item);
 
       // If we unexpanded while having something selected our total number of
       // rows is less than the num visible rows, then make sure we show all the
@@ -4309,7 +4319,7 @@ class ThreadsTreeDelegate : public TreeDelegate {
 public:
   ThreadsTreeDelegate(Debugger &debugger)
       : TreeDelegate(), m_thread_delegate_sp(), m_debugger(debugger),
-        m_stop_id(UINT32_MAX) {
+        m_stop_id(UINT32_MAX), m_update_selection(false) {
     FormatEntity::Parse("process ${process.id}{, name = ${process.name}}",
                         m_format);
   }
@@ -4337,6 +4347,7 @@ public:
 
   void TreeDelegateGenerateChildren(TreeItem &item) override {
     ProcessSP process_sp = GetProcess();
+    m_update_selection = false;
     if (process_sp && process_sp->IsAlive()) {
       StateType state = process_sp->GetState();
       if (StateIsStoppedState(state, true)) {
@@ -4345,6 +4356,7 @@ public:
           return; // Children are already up to date
 
         m_stop_id = stop_id;
+        m_update_selection = true;
 
         if (!m_thread_delegate_sp) {
           // Always expand the thread item the first time we show it
@@ -4356,11 +4368,15 @@ public:
         TreeItem t(&item, *m_thread_delegate_sp, false);
         ThreadList &threads = process_sp->GetThreadList();
         std::lock_guard<std::recursive_mutex> guard(threads.GetMutex());
+        ThreadSP selected_thread = threads.GetSelectedThread();
         size_t num_threads = threads.GetSize();
         item.Resize(num_threads, t);
         for (size_t i = 0; i < num_threads; ++i) {
-          item[i].SetIdentifier(threads.GetThreadAtIndex(i)->GetID());
+          ThreadSP thread = threads.GetThreadAtIndex(i);
+          item[i].SetIdentifier(thread->GetID());
           item[i].SetMightHaveChildren(true);
+          if (selected_thread->GetID() == thread->GetID())
+            item[i].Expand();
         }
         return;
       }
@@ -4368,12 +4384,42 @@ public:
     item.ClearChildren();
   }
 
+  void TreeDelegateUpdateSelection(TreeItem &root, int &selection_index,
+                                   TreeItem *&selected_item) override {
+    if (!m_update_selection)
+      return;
+
+    ProcessSP process_sp = GetProcess();
+    if (!(process_sp && process_sp->IsAlive()))
+      return;
+
+    StateType state = process_sp->GetState();
+    if (!StateIsStoppedState(state, true))
+      return;
+
+    ThreadList &threads = process_sp->GetThreadList();
+    std::lock_guard<std::recursive_mutex> guard(threads.GetMutex());
+    ThreadSP selected_thread = threads.GetSelectedThread();
+    size_t num_threads = threads.GetSize();
+    for (size_t i = 0; i < num_threads; ++i) {
+      ThreadSP thread = threads.GetThreadAtIndex(i);
+      if (selected_thread->GetID() == thread->GetID()) {
+        selected_item = &root[i][thread->GetSelectedFrameIndex()];
+        selection_index = selected_item->GetRowIndex();
+        return;
+      }
+    }
+  }
+
   bool TreeDelegateItemSelected(TreeItem &item) override { return false; }
 
+  bool TreeDelegateExpandRootByDefault() override { return true; }
+
 protected:
   std::shared_ptr<ThreadTreeDelegate> m_thread_delegate_sp;
   Debugger &m_debugger;
   uint32_t m_stop_id;
+  bool m_update_selection;
   FormatEntity::Entry m_format;
 };
 

lldb/test/API/commands/gui/expand-threads-tree/Makefile

@@ -0,0 +1,3 @@
+C_SOURCES := main.c
+ENABLE_THREADS := YES
+include Makefile.rules

lldb/test/API/commands/gui/expand-threads-tree/TestGuiExpandThreadsTree.py

@@ -0,0 +1,55 @@
+"""
+Test the 'gui' default thread tree expansion.
+The root process tree item and the tree item corresponding to the selected
+thread should be expanded by default.
+"""
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.lldbpexpect import PExpectTest
+
+class TestGuiExpandThreadsTree(PExpectTest):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    # PExpect uses many timeouts internally and doesn't play well
+    # under ASAN on a loaded machine..
+    @skipIfAsan
+    @skipIfCursesSupportMissing
+    def test_gui(self):
+        self.build()
+
+        self.launch(executable=self.getBuildArtifact("a.out"), dimensions=(100,500))
+        self.expect("breakpoint set -r thread_start_routine", substrs=["Breakpoint 1", "address ="])
+        self.expect("run", substrs=["stop reason ="])
+
+        escape_key = chr(27).encode()
+
+        # Start the GUI and close the welcome window.
+        self.child.sendline("gui")
+        self.child.send(escape_key)
+        self.child.expect_exact("Threads")
+
+        # The thread running thread_start_routine should be expanded.
+        self.child.expect_exact("frame #0: thread_start_routine")
+
+        # Exit GUI.
+        self.child.send(escape_key)
+        self.expect_prompt()
+
+        # Select the main thread.
+        self.child.sendline("thread select 1")
+
+        # Start the GUI.
+        self.child.sendline("gui")
+        self.child.expect_exact("Threads")
+
+        # The main thread should be expanded.
+        self.child.expect("frame #\d+: main")
+
+        # Quit the GUI
+        self.child.send(escape_key)
+
+        self.expect_prompt()
+        self.quit()

lldb/test/API/commands/gui/expand-threads-tree/main.c

@@ -0,0 +1,10 @@
+#include <pthread.h>
+
+void *thread_start_routine(void *arg) { return NULL; }
+
+int main() {
+  pthread_t thread;
+  pthread_create(&thread, NULL, thread_start_routine, NULL);
+  pthread_join(thread, NULL);
+  return 0;
+}